U.S. troops sit on the top of a military vehicle as their convoy passes near Malu village, Romania May 13, 2015. Reuters/Ovidiu Micsik/Inqua Photos

The balance of military power in the Asia-Pacific is shifting against the United States, as China and North Korea challenge the credibility of U.S. security commitments and the Pentagon faces spending limits, according to a study released on Tuesday.

Researchers at the Center for Strategic and International Studies, which conducted the study for the U.S. Department of Defense, were left "concerned" that President Barack Obama's "rebalance" of U.S. interests toward Asia might not be sufficient to secure U.S. interests in the region.

Congress required the Department of Defense to commission the report under the 2015 National Defense Authorization Act.

"Chinese and North Korean actions are routinely challenging the credibility of U.S. security commitments, and at the current rate of U.S. capability development, the balance of military power in the region is shifting against the United States," the study said.

Pentagon leaders, and supporters in Congress, say efforts to keep pace with China's growing military might and other international security threats have been hampered by mandatory "sequestration" budget cuts imposed across the government in 2011 in an effort to address the massive U.S. deficit.

Congress passed a spending bill at the end of 2016 that addressed some of those concerns, but has not come up with a long-term solution.

The report makes four recommendations.

The first is that the White House should develop a single rebalance strategy, after finding confusion throughout the government. Among other things, the report said the administration should increase its outreach to Congress and coordinate better with allies.

The second recommendation is that Washington should accelerate efforts to strengthen its allies and partners, including in the area of maritime security. "Many states are struggling to mitigate regional security risks that range from major humanitarian crises to maritime disputes to missile threats," the study said.

The third recommendation is that the United States should sustain and expand its military presence in the Asia-Pacific, and the fourth was that the United States should accelerate development of new capabilities for U.S. forces, such as the ability to resist the growing ballistic missile threat to U.S. ships and forward bases.